Port and Radiation Pattern Decoupling of Single-Layer SIW Cavity-Based Slot Antennas

A cavity-based decoupling method is presented to obtain port decoupling (PD) and radiation pattern decoupling (RPD) simultaneously for slot antennas. Placing two rectangular waveguides side by side and removing their shared side wall will form a rectangular cavity. By fine tuning the cavity, its travelling TE₁₀ and TE₂₀ modes can be superposed to obtain transmission zeros at desired frequency, namely high isolation or PD. Introducing slot in the excited waveguide path will further superpose the field and prevent energy from flowing into the coupled path. Therefore, there is little energy for the symmetric slot in the coupled path to radiate, and then RPD can be obtained. To verify the effectiveness of this decoupling method, two-port substrate-integrated waveguide (SIW) slot array antenna is designed, fabricated, and measured. The measured overlapping bandwidth of 10-dB impedance bandwidth and 25-dB isolation bandwidth is 1.4%. It should be highlighted that typical unidirectional radiation patterns along the zenith direction are obtained, implying the RPD characteristic. This SIW slot array antenna design uses only one-layer substrate, which makes it low-profile and integration-friendly.